Improvement in blackboard-erasers



@ummm lllll x l l l l l x I l mUNITED STATES FRANK G. JOHNSON, OF BROOKLYN, NEW YORK.

IMPROVEMENT IN BLACKBOARD-SERASERSg Specification forming part of Letters Patent No. 128,149, dated J une 18, 1872.

To all whom trudy concern:

Be it known that I, FRANK G. J oHNsoN, of Brooklyn, in the county of Kings and State of New York, have invented a new and Improved Eraser for Bla-ckboards, Src.; and I do hereby declare that the following is a full, clear, and exact description thereof, which will enable others skilled in the art to make and use the same, reference being' had tothe accompanying drawing forming part of this specification.

My invention relates to a new and useful eraser for use on blackboards, slates, and the like, for erasing iigures and other marks; and it consists in a holder of novel construction,

vadapted to hold a number of sheets of woven,

felted, or other fibrous substances, so that said sheets may be held and sustained suitably for doing the rubbing at the edges and by the ends of the threads or ibers exposed thereat, so as to utilize the great capacity of such substances to resist wear. In this way these comparatively cheap substances arev equal or nearly so to bristles, which are more expensive, while the said substances are better in some respects for these uses than bristles, besides being an excellent substitute for chamois-skin for cleaning and polishing silver and other metal ware. They are also useful for washing carriages and windows, for which spqnges are generally used, and are much cheaper and more durable than sponges.

Figure lis partly a side elevation and partly a sectional elevation of my improved eraser, and Fig. 2 is a transverse section of the same.

Similar letters of reference indicate correon both sides, and to occupy an amount of space equal to the compression of the sheets, so that the parts of the sheets D which project a little beyond the lower edges to do the rubbing, will be free from compression, and

not be caused to spread out sidewise, as they would without the said plates F. For these sheets D I prefer to use thick woven cotton goods, such as indicated in the drawing, or felted goods of wool of about equal thickness, but thinner pieces will do, using thinner plates F; or two or more sheets of the rubbing substance may be placed between the plates. I prefer the thicker sheets, however. The sheets of fibrous substance being used in this way are much more efficient than when so used that the sides are brought in contact with the blackboard, besides withstanding the wear so much better. They are also much more durable than sponge or skin while they are equally efficient. The said sheets are not to project so far beyond thc jaws A that they can be turned over by pressure against the blackboard, so that the sides will be brought in contact with the board.

For an instrument to be used for washing carriages, windows, or ioors, I would use galvanized metal 'clamping-plates A, or other metal that will not be materially affected by the alkaline substances used.

lt will be seen that the back C causes the sheets to be compressed slightly more at. the edges of the clamps from which they project than'above, and that, in consequence of the upper edges being prevented from coming together by said back piece, the said sheets will be held securely, while decreasing in width y and being shifted forward in the jaws from time to time, until they are but little wider than the amount they project.

Having thus described my invention, I claim as new and desire to secure by Letters Patentf- An erasing or rubbing instrument, consisting of a series of sheets of woven or felted cotton, wool, or vegetable fiber, and a holder therefor, said sheets being conned by said holder in such manner that the rubbing is effected by the ends of the bers exposed at the cut edges of the said sheets projecting from the holder, substantially as shown and specified.

FRANK G. JOHNSON.

Witnesses:

GEo. W. MABEE, ALEX. F. ROBERTS. 

